The house I live in was built sometime in the early 1900’s, in fact with one exception all the houses I’ve lived in were built between 1850 and 1925. They weren’t built with indoor bathrooms or central heating, they weren’t designed for the most part with running water in mind at all, which is why so many British kitchens have washing machines in the kitchen!
They aren’t great at retaining heat in winter or staying cool in summer either and as my flat is a conversion, it’s all that with no outdoor space. Which means that the bathroom and the bedroom where I dry clothes can get mould. It’s not a huge amount of mould. In the bathroom it’s on the tile grouting and in the bedroom it’s on the wall that the airer stands when I’m drying things and it’s just on the surface.
I’m pretty good about leaving the window open in those rooms but every couple of months, I use this, just to keep things clean and stop the mould getting a grip of walls. It has bleach in it, so careful of your clothes when you’re using it, but it works better than using just bleach would because I’ve tried that!